FARMERS in the Central Midlands region are concerned about the high number of locusts on their properties.
Growers in Miling, Coomberdale and Wongan Hills have reported increased activity, and with seeding underway, there are fears the pest may pose a risk to crops as they germinate.
The Department of Agriculture and Food WA (DAFWA) has conducted autumn locust surveys on more than 470 sites across the State’s agricultural region, and in general, the results show low to very low population densities of Australian plague locust (APL).
However, DAFWA entomologist Svetlana Micic said this species was not the only one causing concern.
“What is different this year is that we do have mixed populations present,” Ms Micic said.
“North of Moora we’ve had reports of APL and yellow wings present in the same paddock, in the southern areas we’ve also had wingless grasshoppers present in paddocks with APL, and in parts we’ve had the small plague locust present with APL.”
Ms Micic said high summer rainfall had created ideal conditions for APL and other locust and grasshopper species to thrive.
“We always have a residual population of APL, but what happened in January and February 2017 is that we had a large rain event in large parts of the landscape and that made it nice and green, so then we’ve had this background population which has increased in numbers,” she said.
“Those adults will have laid eggs, they’re in numbers to be concerning to germinating crops but not in numbers to be concerning for widespread movement of locusts.
“It’s green plant material that they’ll feed on, so in localised areas people are going to have issues but locust damage is always patchy, so just because locusts are present in a paddock it doesn’t necessarily mean that they will cause crop damage.”
It is expected that locust numbers will diminish as winter approaches, with wet and cooler conditions limiting their mobility.
Ms Micic has urged growers to monitor emerging crops for APL, and apply insecticide if damage has been inflicted.
She said while a number of chemicals were registered for locust control, synthetic pyrethroids used in knockdown mixes did not have residual to protect crops at emergence.
“Paddocks do need to monitored, especially paddocks that are next to or adjacent to a paddock which has locusts in it,” she said.
“If you know that they’re present you do need to spray, and it’s the timing of the sprays that’s important.
“You want to apply the insecticides when the grasshoppers are actually present on the paddock, if you can do that when it’s going to be a warm day, early in the morning you’ll get better kill.
“You’ll get more insecticide onto the locust and then they’ll be actively moving, and you’ll get better kill with them coming into contact with or feeding on insecticide covered vegetation.
“One of the big things to stress is that you need to identify what you’ve got in your paddocks to make sure that you’re applying the correct rate of insecticide because some of our large grasshopper species do require different insecticide rates than the APL.”
